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Abstract:

A toothed chain, which has a multiplicity of toothed links and cover
links articulatedly connected to one another by cradle pieces. The cradle
pieces are arranged in cradle piece openings of the toothed links and
cover links. The cover links form guide links situated at the outside at
both sides of a longitudinal direction and hold the toothed links between
them. The cover links are formed with link yokes, which have a respective
opening for the cradle pieces, and with an upper and lower link web which
connect the link yokes. An opening is formed in the region between the
upper and lower link webs, which has, in plan view, a substantially
trapezoidal shape with sides of substantially equal lengths and an upper
side and lower side of different lengths. The upper side is assigned to
the upper link web and the lower side to the lower link web.

Claims:

1-11. (canceled)

12. A toothed chain for a vehicle drive, comprising: cradle pieces
running substantially transversely with respect to a longitudinal
direction of the toothed chain; a multiplicity of toothed link plates
having cradle piece openings; and cover link plates having cradle piece
openings, an upper link plate web, a lower link plate web, an opening
formed between the upper link plate web and the lower link plate web, and
link plate hoops which have the cradle piece openings, the upper link
plate web and the lower link plate web connecting the link plate hoops,
the cover link plates being articulatedly connected to one another by the
cradle pieces, which are arranged in the cradle piece openings of the
toothed link plates and the cover link plates, and the cover link plates
forming guide link plates, which are situated at an outside, at both
sides of the longitudinal direction of the toothed chain with the toothed
link plates being held between the guide link plates, wherein the opening
of the cover link plates has a shape which is substantially trapezoidal
in plan view with sides of substantially equal length in a height
direction of the opening and a top side and an underside of different
lengths in a width direction of the opening with the top side being
longer than the bottom side and with the top side assigned to the upper
link plate web and the underside assigned to the lower link plate web.

13. The toothed chain as claimed in claim 12, wherein the top side is
concavely curved toward the upper link plate web proceeding from the
opening, and the underside is concavely curved toward the lower link
plate web proceeding from the opening.

14. The toothed chain as claimed in claim 12, further comprising
concavely formed upper and lower connecting regions between the sides,
the top side and the underside of the opening, and the sides of the
opening in the height direction of the opening being substantially
rectilinear.

15. The toothed chain as claimed in claim 12, wherein the upper link
plate web has a smallest width in the height direction of the opening and
the lower link plate web has a greatest width in the height direction of
the opening, and a ratio of the smallest width in the height direction of
the upper link plate and the greatest width in the height direction of
the lower link plate has a value in a range of approximately 0.2 to
approximately 0.4.

16. The toothed chain as claimed in claim 15, wherein the ratio of the
smallest width in the height direction of the upper link plate and the
greatest width in the height direction of the lower link plate is
approximately 0.4.

17. The toothed chain as claimed in claim 14, wherein the opening has
concave recesses formed in the upper and lower connecting regions between
the top side, the underside and one of the sides of the opening, the
concave recesses are directed outwardly and toward the opening and have a
first radius of curvature, and in a region between the recesses, are
formed so as to be concavely curved with a second radius of curvature in
the direction of the opening, and the first radius of curvature is
smaller than the second radius of curvature.

18. The toothed chain as claimed in claim 12, further comprising a
connecting web, which connects the upper link plate web and the lower
link plate web, formed between the cradle piece openings and the opening,
the connecting web has a side region directed toward the opening which
forms an angle with the height direction of the opening, the angle has a
value in a range of approximately 8 degrees to approximately 12 degrees.

19. The toothed chain as claimed in claim 18, wherein the angle is
approximately 10 degrees.

20. The toothed chain as claimed in claim 18, wherein the opening has
upper transition regions located between the top side and the sides of
the opening and lower transition regions located between the underside
and the sides of the opening, wherein the connecting web has an upper
recess formed between the top side and the one of the sidewalls, which
faces the opening and a lower recess formed between the bottom side and
the one of the sidewalls, which faces the opening, and wherein the
connecting web has a first width in a region between the upper recess of
the cradle piece opening and the upper transition region of the opening
and a second width in a region between the lower recess and the lower
transition region of the opening, a ratio of the first width of the
connecting region to the second width of the connecting region has a
value in a range from approximately 0.8 to approximately 1.2.

21. The toothed chain as claimed in claim 20, wherein the ratio of the
first width of the connecting region to the second width of the
connecting region has a value of 0.9.

22. The toothed chain as claimed in claim 18, wherein the opening has
upper transition regions located between the top side and the sides of
the opening and lower transition regions located between the underside
and the sides of the opening, the opening, as viewed in the width
direction of the opening, has a width between the upper transition
regions and a width between the lower transition regions, a ratio of the
upper transition regions to the lower transition regions has a value in a
range from approximately 1.0 to approximately 1.3.

23. The toothed chain as claimed in claim 22, wherein the ratio of the
upper transition regions to the lower transition regions has a value of
1.19.

24. The toothed chain as claimed in claim 12, wherein the opening has
upper transition regions located between the top side and the sides of
the opening and lower transition regions located between the underside
and the sides of the opening and the toothed chain has a pitch, and the
opening as viewed in the height direction of the opening, has a height
which corresponds approximately to 0.6 times the pitch of the toothed
chain.

25. The toothed chain as claimed in claim 24, wherein the opening, as
viewed in the height direction of the opening, has a distance between the
upper transition regions and the lower transition regions, and a ratio of
the distance between the upper transition regions and the lower
transition regions to the height of the opening has a value in the range
from approximately 0.1 to approximately 1.0.

26. The toothed chain as claimed in claim 25, wherein the opening has a
value of 0.567.

27. The toothed chain as claimed in claim 12, further comprising
additional openings which connect the opening and the cradle piece
openings.

Description:

[0001] This application is a continuation of PCT/DE2009/001345 filed Sep.
24, 2009, which in turn claims the priority of U.S. Provisional Patent
Application No. 61/197,236 filed Oct. 25, 2008, the priority of both
applications is hereby claimed and both applications are incorporated by
reference herein.

FIELD OF THE INVENTION

[0002] The present invention relates to a toothed chain, in particular for
a vehicle drive, having a multiplicity of toothed link plates and cover
link plates articulatedly connected to one another by cradle pieces.

[0003] Such toothed chains may be used for example in transfer gearboxes
or very generally in gearboxes in which shaft distances must be overcome.

BACKGROUND OF THE INVENTION

[0004] In such toothed chains, use is made of different link plate types,
since the toothed chain must be guided transversely with respect to its
direction of circulation. For this purpose, the chain has integrated into
it so-called guide link plates or cover link plates which, in the case of
externally-guided toothed chains, are provided with a run-in web which
projects laterally beyond the sprocket which interacts with the toothed
chain.

[0005] With such guide link plates, it must be ensured that the rigidity
of the guide link plate does not differ significantly from the rigidity
of the toothed link plates situated at the inside. Specifically, if there
is a significant difference here, then the guide link plates or cover
link plates absorb higher tensile stresses and therefore cause higher
stresses at the stress-critical regions, specifically in the contact
region between the cover link plate and the cradle pieces pressed into
the cradle piece openings, such that there is the risk of crack formation
proceeding from these then overloaded regions. To eliminate said problem,
known guide link plates have an opening in the region between the upper
and lower link plate webs. Said opening serves to reduce the rigidity of
the cover link plate.

[0006] For said guide link plates, a plurality of embodiments has already
been disclosed in the prior art. For example, U.S. Pat. No. 5,345,753 has
disclosed a guide link plate which, in the region between the upper and
lower link plate webs, has an opening composed of a plurality of
interconnected convex or concave curve segments. In said known cover link
plate, the upper link plate web has a greater width than the lower link
plate web, resulting in a non-uniform tensile force distribution; the
upper link plate web absorbs a significantly greater tensile force than
the lower link plate web.

[0007] Furthermore, the configuration of the opening with a plurality of
concave or convex curve segments has the result that said opening can be
produced only with difficulty. Such cover link plates are usually
produced by means of a punching tool; on account of the complex
configuration of the opening, bending of the edge regions of the opening
and/or distortion of the link plates occurs as the inner opening is
punched out.

[0008] A similar problem is also encountered with the cover link plate
known from U.S. Pat. No. 6,171,209, which has a bone-shaped opening and
which can likewise be produced only with difficulty on account of the
alternating convex and concave curve segments.

[0009] Finally, U.S. Pat. No. 5,176,586 has disclosed a cover link plate
whose opening between the cradle piece openings has an elongate oval
configuration and in which the upper link plate web is formed so as to be
significantly wider than the lower link plate web, that is to say there
is again a non-uniform tensile force distribution with the result that
the stress-critical points of the cradle piece openings are again
subjected to non-uniform loading, and there is the risk of cracks forming
proceeding from the contact zone between the cradle piece and the cradle
piece opening.

[0010] The known cover link plates thus have the problem that, on account
of their rigidity, they lead to non-uniform stress distributions in the
toothed chain.

SUMMARY OF THE INVENTION

[0011] Taking this as a starting point, the object on which the present
invention is based is that of providing a toothed chain which has cover
link plates and which leads to a more uniform stress distribution in the
region of the stress-critical points than is obtained in toothed chains
having the known cover link plates.

[0012] The invention provides a toothed chain, in particular for a vehicle
drive, having a multiplicity of toothed link plates and cover link plates
articulatedly connected to one another by means of cradle pieces, the
cradle pieces running substantially transversely with respect to the
longitudinal direction of the toothed chain and being arranged in cradle
piece openings of the toothed link plates and cover link plates, and the
cover link plates forming guide link plates which are situated at the
outside at both sides of the longitudinal direction of the toothed chain
and which hold between them the toothed link plates, and said cover link
plates being formed with link plate hoops which have a respective opening
for the cradle pieces and with an upper link plate web and a lower link
plate web which connect the link plate hoops, and an opening being formed
in the region between the upper and lower link plate webs, wherein the
opening has a shape which is substantially trapezoidal in plan view and
which has sides of substantially equal length in a height direction of
the opening and which has a top side and an underside of different
lengths in a width direction of the opening, and the longer top side is
assigned to the upper link plate web and the shorter underside is
assigned to the lower link plate web.

[0013] The invention is thus characterized in that the special shape of
the opening in conjunction with the upper and lower link plate webs
generates between the mutually adjacently arranged joints of the toothed
chain a force flow which leads to a significantly more uniform stress
distribution between the upper and lower stress-critical points in the
contact zones of the cradle pieces with the cradle piece openings than is
obtained in the known toothed chains with the known, above-described
cover link plates.

[0014] Those sides of the trapezoidal recess or opening of the cover link
plate which are assigned to the respective cradle piece openings are in
each case of substantially equal length; the top side which is assigned
to the upper link plate web is longer than the underside, which is
assigned to the lower link plate web, of the opening. It has been found
that said trapezoidal shape of the opening leads to a surprisingly good
substantially uniform distribution of the compressive stresses in the
region of the upper and lower contact zone of the cradle piece with the
cradle piece openings of the cover link plate. Said substantially uniform
distribution then in turn ensures that, in loading situations, no one
point of the contact zones is at a greater risk of cracking than adjacent
points of the contact zone, and therefore the probability of failure of
the toothed chain has been reduced and therefore the service life of the
toothed chain according to the invention has been lengthened.

[0015] In one refinement of the invention, the top side of the opening is
formed so as to be concavely curved toward the upper link plate web
proceeding from the opening, and the underside is likewise formed so as
to be concavely curved toward the lower link plate web proceeding from
the opening. Said configuration serves to reduce the width of the upper
and lower link plate webs, and therefore to reduce the rigidity of the
cover link plate, and therefore in turn to prevent the cover link plates
from undesirably absorbing a considerably greater ensile force than the
toothed link plates arranged within the cover link plates, and therefore
the risk of damage to the cover link plates in the region of the
stress-critical points of the contact zones is reduced.

[0016] In one refinement of the invention, the two sides of the opening
are of substantially rectilinear design and have in each case concavely
formed upper and lower connecting regions, as viewed in the outward
direction proceeding from the opening, between them and the top side and
the underside. Said configuration has the result that no stress
concentration occurs at corner regions of the opening, which in turn
would promote the risk of crack formation.

[0017] In one refinement of the invention, the opening of the cover link
plates is formed such that the upper link plate web has a smallest width
A as viewed in the height direction of the opening and the lower link
plate web has a maximum width C as viewed in the height direction of the
opening, and the ratio A/C has a value in the range from approximately
0.2 to approximately 0.4 and in particular of 0.3. It has been found
that, with the cover link plate according to the invention having these
value ratios, a balanced stress distribution can be attained in the
region of the critical contact zones between the cradle pieces and the
cradle piece openings.

[0018] In one refinement of the invention, the cradle piece openings, at
their regions situated at the top and bottom in the height direction of
the opening and facing toward the opening, have in each case a concave
recess which is directed outwardly and toward the opening and which has a
first radius of curvature, and in the region between the recess, are
formed so as to be concavely curved with a second radius of curvature in
the direction of the opening, the first radius of curvature being smaller
than the second radius of curvature. Said configuration of the cradle
piece openings with the recesses has the effect that, as the toothed
chain circulates around the sprockets, the cradle pieces have a
deflection space, and no undesirable stress build-up with locally high
stress peaks occurs between the cradle pieces and the cradle piece
openings.

[0019] It is also provided in one refinement of the invention that in each
case one connecting web which connects the upper link plate web and the
lower link plate web is formed between the cradle piece openings and the
opening, that side region of which connecting web which is directed
toward the opening encloses an angle a with the height direction of the
opening, which angle a has a value in the range from approximately 8
degrees to approximately 12 degrees and in particular of approximately 10
degrees. Said angle range has likewise proven to be advantageous for
preventing the formation of local stress peaks and for providing a
balanced stress distribution in the region of the connecting web and the
cradle piece openings. Here, the connecting web has a substantially
constant width in the region between the upper link plate web and the
lower link plate web, such that said connecting web, along its
longitudinal extent as viewed in the height direction of the opening
between the upper link plate web and the lower link plate web, undergoes
a change in width of only approximately 20 percent.

[0020] Assuming that the connecting web has a width B1 in the region
of the upper recess of the cradle piece opening in the upper connecting
region between the first and second radii of curvature of the cradle
piece opening and of the facing side of the opening, and has a width
B2 in the region of the lower recess in the lower transition region
between the first and second radii of curvature of the cradle piece
opening and of the facing side of the opening, the ratio B1/B2
should be within a value range from approximately 0.8 to approximately
1.2 and in particular of 0.9. Said value range, too, has proven to be
advantageous with regard to obtaining a balanced stress distribution in
the region of the critical contact zones.

[0021] The cradle piece openings thus each have an upper and lower
transition region between the in each case first and second radii of
curvature. In one refinement of the invention, it is provided that the
opening, as viewed in the width direction of the opening, has a width
F1 between the two upper transition regions of the two cradle piece
openings and has a width F2 in the region between the two lower
transition regions, and the ratio F1/F2 has a value in the
range from approximately 1.0 to approximately 1.3, and in particular of
1.19.

[0022] Furthermore, it has proven to be advantageous for the height D of
the opening as viewed in the height direction of the opening to have a
value which approximately corresponds to 0.6 times the pitch P of the
toothed chain. Furthermore, the opening, as viewed in the height
direction, has a distance E between the upper and lower abovementioned
transition regions, and according to the invention, the ratio E/D has a
value in the range from approximately 0.1 to approximately 1.0, with a
value of 0.567 having proven to be particularly advantageous.

[0023] Finally, in one refinement of the invention, it is also provided
that the opening and the cradle piece openings are connected to
additional openings which connect said respective openings, so as to form
an integral opening which is determined substantially by the contour of
the cradle piece openings and the openings, which is advantageous in
particular with regard to production with a single-piece punching die.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will be explained in more detail below on the basis
of the drawing, in which:

[0025] FIG. 1 shows a plan view of a toothed chain as per an embodiment
according to the present invention, with toothed link plates and with
cover link plates arranged at the outside at both sides of the
longitudinal direction of the toothed chain;

[0026] FIG. 2 shows a view of a cover link plate of a toothed chain
according to the present invention;

[0027] FIG. 3 shows a view similar to that in FIG. 2, but showing a
modified cover link plate;

[0028] FIG. 4 shows an enlarged illustration of the cover link plate as
per FIG. 2, with labels for explaining the geometric relationships;

[0029] FIG. 5 shows an illustration similar to FIG. 4, with further labels
for explaining the geometric relationships, and

[0030] FIG. 6 shows an illustration similar to FIG. 5, with further labels
for explaining the geometric relationships.

DETAILED DESCRIPTION OF THE INVENTION

[0031] FIG. 1 of the drawing shows, in a view from above, a toothed chain
1 having a multiplicity of inner toothed link plates 2 arranged offset
with respect to one another, and having cover link plates or guide link
plates 3 arranged in the longitudinal direction L at both sides of the
toothed chain 1. The toothed link plates 2 and the cover link plates 3
are articulatedly connected to one another in each case by means of
cradle pieces 4 arranged substantially transversely with respect to the
longitudinal direction of the toothed chain 1.

[0032] The design of the cover link plates 3 is shown in more detail in
FIG. 2.

[0033] The cover link plates 3 have cradle piece openings 5 in which the
cradle pieces 4 already mentioned above are arranged. An opening 6 is
arranged between the two cradle piece openings 5 which are arranged one
behind the other in the longitudinal direction L of the toothed chain 1,
which opening 6 is of trapezoidal design in the side view of the cover
link plate 3 (if the link plate 3 lies on a flat surface, then the
illustration also corresponds to a plan view of the cover link plate 3).

[0034] Here, the opening 6 has a top side 9 assigned to an upper link
plate web 7 and has an underside 10 assigned to a lower link plate web 8.
The upper link plate web 7 and the lower link plate web 8 are connected
by two link plate hoops 11 in which the cradle piece openings 5 are
formed. The top side 9 and the underside 10 are adjoined in each case by
connecting regions which connect the top side 9 and the underside 10 to
rectilinear sides 12 of the opening 6.

[0035] Here, the upper connecting regions 13 connect the top side 9 to the
sides 12, and the lower connecting regions 14 connect the underside 10 to
the sides 12, and as viewed from the opening 6, the connecting regions
13, 14 are concavely curved in the outward direction.

[0036] A run-in web 15 prevents lateral slippage of the toothed chain 1 as
it circulates around sprockets (not illustrated in any more detail). The
cradle piece openings 5 each have, at their sides facing toward the upper
link plate web 7 and the lower link plate web 8, recesses 16 which are
concavely curved in the direction of the opening 6 and of the link plate
webs 7, 8.

[0037] In each case one connecting web 17 is formed between the cradle
piece openings 5 and the opening 6, one side of which connecting web 17
in the lateral direction is delimited by the side 12 of the opening 6 and
the other side of which connecting web 17 in the lateral direction is
delimited by the cradle piece opening 5.

[0038] FIG. 3 of the drawing shows a modified embodiment of a cover link
plate 3, which differs from the cover link plate 3 illustrated in FIG. 2
substantially in that, in addition to the opening 6 and the cradle piece
openings 5, there are provided two further openings 18 which connect said
openings, such that a continuous opening is formed whose main opening is
however, like before, the trapezoidal opening 6. The continuous opening
has the advantage that, during production, only a single die is required
for the punching process. In the further illustration, more detail will
be given regarding the cover link plate 3 illustrated in FIG. 2, in order
to describe the geometric relationships in particular of the opening 6
and of the connecting web 17.

[0039] As can be seen from the enlarged illustration of FIG. 4, the cradle
piece opening 5, proceeding from the cradle piece opening 5, has the
recess 16 which is formed concavely with a first radius of curvature, and
said cradle piece opening 5 is likewise formed concavely in the direction
of the opening 6 with a second radius of curvature, specifically in the
region of the reference symbol 19. Here, the first radius of curvature is
significantly smaller than the second radius of curvature. The transition
region from the first radius of curvature to the second radius of
curvature and back to the first radius of curvature indicates in each
case a transition region 20 and a transition region 21 respectively, at
which high compressive stresses occur during the rolling of the cradle
pieces 4.

[0040] As can be seen from FIG. 4, the connecting web 17 is inclined by an
angle a of approximately 10 degrees relative to the height direction of
the opening 6. The connecting web 17 has a width B1 at the upper
transition region 20 and has a width B2 at the lower transition
region 21. In the embodiment illustrated, the ratio B1/B2 of
the width B1 to the width B2 is approximately 0.9.

[0041] The upper link plate web 7 has a width A transversely with respect
to the longitudinal direction L, and the lower link plate web 8 has a
width C. In the illustrated embodiment, the ratio A/C is approximately
0.3.

[0042] FIG. 5 of the drawing shows the opening 6 with further labels for
explaining the geometric relationships. As is readily apparent from FIG.
5, the opening 6, as viewed in the width direction of the opening, has a
width F1 between the upper transition regions 20 of the cradle piece
opening 5, and has a width F2 slightly below the lower transition
region 21. In the illustrated embodiment of the cover link plate 3, the
ratio F1/F2 has the value 1.19. Proceeding from the measurement
height for the width F1, the width F2 is determined a distance
E below the measurement height for the width F1. The opening 6, as
viewed in the height direction, has a height D, and in the illustrated
embodiment, the ratio E/D between the distance E and the height D is
0.567. Here, the height D corresponds approximately to 0.6 P, wherein P
represents the pitch of the toothed chain 1.

[0043] The opening 6 can be paraphrased as a trapezoid 22 shown in more
detail on the basis of FIG. 5. A line G1 is applied to the top side
9 and a line G2 is applied to the underside 10. The distance between
said two lines corresponds to the height D already mentioned above. The
length of said two lines in each case to the point of intersection with
lines 23 applied to the two sides 12 is measured. In the illustrated
embodiment, the ratio G1/G2 is approximately 1.38, wherein
values of said ratio from approximately 1 to approximately 1.5 have
proven to be advantageous.

[0044] The cover link plate 3 has a total height H. In the illustrated
embodiment, the ratio D/H of the height D of the opening 6 to the total
height H of the cover link plate 3 is approximately 0.52, wherein values
in the range from 0.3 to 0.8 have proven to be advantageous.

[0045] If a central line 24 is drawn between the two parallel sides of the
trapezoid 22, then said central line 24 is at a distance J from the
central line 25 of the entire cover link plate 3 (corresponds to the
parting plane, specifically the connection of the joint contact points in
the straight chain strand). Said distance J amounts to approximately 2 to
approximately 5 percent of the pitch P.

[0046] The toothed chain according to the invention is characterized in
that it has a more uniform force distribution between the toothed link
plates and the cover link plates, because the cover link plates are
characterized by a targeted manipulation of their rigidity. The opening
of the cover link plate has a trapezoidal configuration and leads to a
balanced stress distribution at the stress-critical points.

[0047] The configuration of the toothed chain according to the invention
with the cover link plates described in more detail leads to a material
saving and therefore to a weight saving of the toothed chain in relation
to known toothed chains. The connecting web has a substantially constant
width, as a result of which the cradle pieces are pressed homogeneously
into the cradle piece openings. Furthermore, an improved supply of oil to
the cover link plates situated at the inside and to the cradle thrust
pieces can be attained via the opening, as a result of which the wear of
the toothed chain according to the invention can be reduced, and
therefore the service life of the toothed chain can be increased.

[0048] With regard to those features of the invention which have not been
explained in any more detail above, reference is otherwise made to the
claims and to the drawings.